Looking at the very first commit of the PR #1273 for PColorMeshItem, the original implementations of width(), height() and boundingRect() were modeled on the implementation for ImageItem, which draws the image at the origin. For ImageItem, the user applies scale and translation transformations to "move" it to the correct spot.

As PColorMeshItem can be drawn with arbitrary coordinates, this model is not appropriate.
A couple of questions:

1. Are width() and height() methods even necessary?
2. And if yes, why return None instead of just zero? (ImageItem returns None, but is there a need to copy ImageItem's interface?)

    def width(self):
        if self.x is None:
            return None
        return len(self.x)

    def height(self):
        if self.y is None:
            return None
        return len(self.y)

    def boundingRect(self):

        if self.z is None:
            return QtCore.QRectF(0., 0., 0., 0.)
        return QtCore.QRectF(0., 0., float(self.width()), float(self.height()))

Would it make sense to force/require the edgecolor pen to be cosmetic? It would simplify the dataBounds method.
It doesn't seem to make sense to draw the polygon edges with a non-cosmetic pen.

Hi @pijyoi sorry for the late response.

I don't think the width and height methods are necessary. I can see the case where having thick lines for the edge-colors would be desired; but I'm not sure it's worth it to support that functionality at the expense of complexity. I would be good with supporting only cosmetic pens. Should add a note about that in the docstring, and maybe put a comment in the code referencing a post here about not supporting non-cosmetic pens.

I can see the case where having thick lines for the edge-colors would be desired; but I'm not sure it's worth it to support that functionality at the expense of complexity. I would be good with supporting only cosmetic pens.

It's okay to support thick cosmetic pens. That code is within pixelPadding. Whether the pen is thick or not, half the pen width still needs to be accounted for.

The code that supports non-cosmetic pens is within dataBounds, and is the code that I would like to remove.

The code that supports non-cosmetic pens is within dataBounds, and is the code that I would like to remove.

I'm good with that.

Thanks @pijyoi for patching up PColorMeshItem! Changes LGTM, merging!